There are known cogeneration systems in which a generator driven by the operation of an engine is used to produce electrical energy, and an exhaust heat exchanger is used to turn cold water into hot water, as disclosed in Japanese Patent Application Laid-Open Publication No. 2006-348948 (JP 2006-348948 A).
A cogeneration system disclosed in JP 2006-348948 A is provided with an engine; a generator that generates electricity, the generator being driven by the operation of the engine; an exhaust heat exchanger for using exhaust heat released from the engine to heat cold water into hot water; a cooling water circulation channel, through which cooling water circulates, and which is disposed between the engine and the exhaust heat exchanger; a cooling water pump for circulating the cooling water, the pump being disposed along the cooling water circulation channel, and a three-way valve for directly returning cooling water from the engine when an air-warming operation is performed immediately after the engine starts.
During the air-warming operation performed immediately after an engine starts, the cooling-water pump is operated, and cooling water from the engine is returned directly to the engine without passing through the exhaust heat exchanger.
In a case where the electrical energy generated by the generator is to be used, the electrical energy will be supplied after the warm-up operation of the engine has concluded; therefore, the cooling water pump cannot be started immediately after the engine has been started. For this reason, when the engine is operated in a power outage and the engine load increases immediately after the engine has started, a cooling water malfunction will occur from the temperature of the cooling water reaching or exceeding a predetermined value, and a risk of engine stoppage will be presented.